Star 6 is a fun beat-making iPhone and iPod Touch app from Agile Partners--makers of the incredibly useful Guitar Toolkit and Tab Toolkit for guitarists. First introduced last August, Star 6 offers five families of electronic drum beats in categories like Drum and Bass and Electro. You can also download many more free beats from the Star 6 Web site, or upload your own through your Web browser. (Your device has to be on the same wireless network as the computer you're uploading through.)

The six triangles at the top of the screen let you switch between beats. The six triangles below them let you control various tonal qualities by tilting your iPhone or iPod Touch toward and away from you.

Once you've picked a family of beats, you can switch among six individual beats, control the speed, and add wacked-out effects like delay and reverse by touching various icons on the screen. It also lets you manipulate tonal qualities such as pitch and gate by tilting the device backward and forward--it uses the iPhone's built-in accelerometer. (The "speed" setting controls the playback speed of the individual sample, not the beats per minute, or BPM, of the entire track.) You can create and name sessions to recall later, and all sessions are automatically saved in the state you left them.

It's a lot of fun to play with, and could be useful in certain professional situations: you could plug your device into an amp or a PA and use it as a simple drum machine, or to fill the gaps between songs in a live or DJ gig, or simply as an audio backdrop for a party.

Version 1.1. of the app, which became available last Friday in the iTunes App Store, adds a number of important usability improvements. First and foremost is something called "quantizing," which helps you switch between rhythms directly on the beat. Before, you had to hit the button at the exact right time, which could be pretty hard when playing a rave track at 170 BPM, otherwise you'd get an awkward transition. The BPM controller is now on the main screen, and has a new feature that lets you slide the rate quickly up and down. You can also have the BPM affect the pitch, in case you want your samples to sound like they've been inhaling helium as you increase the speed of the track.

It's currently available for an introductory price of $6.99, but will go up to $9.99 on January 18, 2010. So if you're interested, jump on it now. For what it's worth, I get a lot of iPhone apps to test out, and this is one of the few that I'll be keeping.